A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a vehicle is equipped with a navigation function to guide a driver to a destination through a calculated route. Such a navigation system detects the position of the user's vehicle, and reads out map data pertaining to an area at the current vehicle position from a data storage medium, for example, a DVD (digital versatile disc), or a hard disc. Typically, the navigation system displays a map image on a monitor screen while superimposing thereon a mark representing the current location of the user's vehicle.
FIGS. 1A-1H show an example of overall procedure and screen display involved in the navigation system for route guidance to a destination. FIG. 1A shows an example of locator map screen of the navigation system when the destination is not specified. Typically, the navigation system displays a street on which the vehicle (current vehicle position VP) is running on a map image and a name of the street. Other information such as a north pointer NP, a map scale and a current time may also be illustrated on the display screen.
When a user selects to set a destination, the navigation system displays a “Find Destination by” screen as shown in FIG. 1B for specifying an input method for selecting the destination. When selecting, the “Point of Interest” method in FIG. 1B, the navigation system displays selection methods of point of interest (POI) either by “Place Name” or “Place Type” in FIG. 1C. If the “Place Type” is selected, the navigation system lists categories of POIs as shown in FIG. 1D.
FIG. 1E shows a screen when the user has selected a “Restaurant” category in FIG. 1D, which includes a list of names of POI type “Restaurant” typically sorted by distance from the current position. The user selects a desired destination, as shown in FIG. 1F and presses an “OK to Proceed” button for the navigation system to calculate an appropriate route to the destination. FIG. 1G shows an example of screen when the navigation system calculates and determines the route to the destination. After determining the route, the navigation system starts the route guidance to the destination as shown in FIG. 1H.
In the operation of the navigation system noted above, typically, a street on which the user's vehicle is running is illustrated with its address. In some geographic areas, a street may run on the boundary (border) line between two or more cities. FIG. 2A is a schematic diagram showing such a situation where a street “Lampson Avenue” is running on a border line between the city of “Stanton” and the city of “Garden Grove”. As shown, the city of “Stanton” is at the north of the street “Lampson Avenue” while the city of “Garden Grove” is at the south.
FIG. 2B shows a typical representation on a screen of the navigation system showing the geographical situation in FIG. 2A. Unless the street is a freeway or its equivalent, a street is usually represented as a single line on the navigation screen. Problems may arise for a street that divides two or more cities as in the example described above under the conventional navigation system.
An example of such problems is a failure to correctly identify a city name based on a street lane on which a vehicle is travelling, i.e., a direction of vehicle. In the example shown in FIG. 2A, the south side of the street is the city of “Garden Grove” and the north side is the city of “Stanton”. Thus, for the vehicle 21 that heads to the east, the street “Lampson Avenue” would be associated with the city of “Stanton” since the vehicle 21 is on the north side of the street under the U.S. traffic regulation. Likewise, for the vehicle 23 that heads to the west, the “Lampson Avenue” would be accompanied by the city of “Garden Grove”.
However, without regard to the direction of travel described above, the conventional navigation system will show one arbitrary city name. In FIG. 2B, even though the vehicle (VP) is heading to the east, a street name window 35 in the map view includes the city name “Garden Grove” rather than “Stanton”. Namely, the navigation system displays the address of the street without taking the direction of the vehicle into consideration.
Another problem is a failure to correctly identify a city name when a street on a map image on the navigation screen is specified when such a street is on the border of two or more cities. FIGS. 3A and 3B show an example of such a situation where the navigation screen shows a street image that divides two cities and two cursor points. This example depicts the situation similar to that of FIGS. 2A and 2B where the street “Lampson Avenue” is on the border line between the city of “Stanton” in the north and the city of “Garden Grove” in the south.
In FIG. 3A, when a cursor on the navigation screen is located at a point 41 that is a northern portion of the street “Lampson Avenue”, the city of “Stanton” would be an appropriate city name. Likewise, in FIG. 3A, for a cursor point 43 that is on a southern portion of the street “Lampson Avenue”, the city of “Garden Grove” would be an appropriate name. However, as shown in FIG. 3B, instead of showing the correct city name, the conventional navigation system will return one city name (either “Stanton” or “Garden Grove”) regardless of the exact location of the cursor point. Thus, in FIG. 3B, even when the cursor is on the point 41, incorrect information is displayed on an address window 45 that includes the city name “Garden Grove” rather than “Stanton”.
Still another problem may arise during a process of finding an address when a particular street is running on a border between two or more cities. FIG. 4A is an example of navigation screen that prompts the user to input an address number (house number) of a desired location. At this stage, the user has already specified the street name of “Lampson” and the address number “8035”, which is an odd number, in an address input field 53 through a keypad 55 on the navigation screen.
In FIG. 4B, based on the street name and address number, the navigation system displays a list of city names in which the candidate location would be found. In this example, although the city names “Garden Grove” and “Stanton” are listed on the screen, there should be only one city that satisfies the input of “8035 Lampson”. Thus, only the city of “Stanton” should be listed supposing that the odd address numbers are assigned to the north side of the street “Lampson Ave”.
Thus, there is a need of a new method and apparatus for a navigation system that is capable of identifying a correct city name associated with a particular street depending on various factors including directions of travel, cursor points, address numbers, etc.